package name.jautzy.esi.server.util;

/*
 * Copyright 2001-2004 The Apache Software Foundation.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

/**
 * Operations to simplifiy common {@link java.security.MessageDigest} tasks.
 * This class is thread safe.
 * 
 * @author Apache Software Foundation
 */
public class DigestUtils {

  /**
   * Returns a MessageDigest for the given <code>algorithm</code>.
   * 
   * @param algorithm
   *          The MessageDigest algorithm name.
   * @return An MD5 digest instance.
   * @throws RuntimeException
   *           when a {@link java.security.NoSuchAlgorithmException} is caught,
   */
  static MessageDigest getDigest(String algorithm) {
    try {
      return MessageDigest.getInstance(algorithm);
    } catch (NoSuchAlgorithmException e) {
      throw new RuntimeException(e.getMessage());
    }
  }

  /**
   * Returns an MD5 MessageDigest.
   * 
   * @return An MD5 digest instance.
   * @throws RuntimeException
   *           when a {@link java.security.NoSuchAlgorithmException} is caught,
   */
  private static MessageDigest getMd5Digest() {
    return getDigest("MD5");
  }

  /**
   * Returns an SHA digest.
   * 
   * @return An SHA digest instance.
   * @throws RuntimeException
   *           when a {@link java.security.NoSuchAlgorithmException} is caught,
   */
  private static MessageDigest getShaDigest() {
    return getDigest("SHA");
  }

  /**
   * Calculates the MD5 digest and returns the value as a 16 element
   * <code>byte[]</code>.
   * 
   * @param data
   *          Data to digest
   * @return MD5 digest
   */
  public static byte[] md5(byte[] data) {
    return getMd5Digest().digest(data);
  }

  /**
   * Calculates the MD5 digest and returns the value as a 16 element
   * <code>byte[]</code>.
   * 
   * @param data
   *          Data to digest
   * @return MD5 digest
   */
  public static byte[] md5(String data) {
    return md5(data.getBytes());
  }

  /**
   * Calculates the MD5 digest and returns the value as a 32 character hex
   * string.
   * 
   * @param data
   *          Data to digest
   * @return MD5 digest as a hex string
   */
  public static String md5Hex(byte[] data) {
    return new String(Hex.encodeHex(md5(data)));
  }

  /**
   * Calculates the MD5 digest and returns the value as a 32 character hex
   * string.
   * 
   * @param data
   *          Data to digest
   * @return MD5 digest as a hex string
   */
  public static String md5Hex(String data) {
    return new String(Hex.encodeHex(md5(data)));
  }

  /**
   * Calculates the SHA digest and returns the value as a <code>byte[]</code>.
   * 
   * @param data
   *          Data to digest
   * @return SHA digest
   */
  public static byte[] sha(byte[] data) {
    return getShaDigest().digest(data);
  }

  /**
   * Calculates the SHA digest and returns the value as a <code>byte[]</code>.
   * 
   * @param data
   *          Data to digest
   * @return SHA digest
   */
  public static byte[] sha(String data) {
    return sha(data.getBytes());
  }

  /**
   * Calculates the SHA digest and returns the value as a hex string.
   * 
   * @param data
   *          Data to digest
   * @return SHA digest as a hex string
   */
  public static String shaHex(byte[] data) {
    return new String(Hex.encodeHex(sha(data)));
  }

  /**
   * Calculates the SHA digest and returns the value as a hex string.
   * 
   * @param data
   *          Data to digest
   * @return SHA digest as a hex string
   */
  public static String shaHex(String data) {
    return new String(Hex.encodeHex(sha(data)));
  }

}
